MANUFACTURING AND USES OF ACTIVE CHARCOAL
Activated charcoal is a carbon that has good absorption ability against anions, cations, and molecules in the form of organic and inorganic compounds, both in the form of solutions and gases. Some materials that contain a lot of carbon and especially those with pores can be used to make activated charcoal. The manufacture of activated charcoal is carried out through the activation process of charcoal by physical or chemical means in the retort.
Differences in raw materials and activation methods used can cause different properties and qualities of activated charcoal. Activated charcoal is used, among others, in the industrial sector (water treatment, food and beverage, cigarettes, chemicals, soaps, scrubs, shampoos, paints and adhesives, masks, refrigeration equipment, automotive), health (absorb toxins in the digestive tract and medicines). ), environment (absorbs metals in wastewater, absorbs pesticide residues in drinking water and soil, absorbs toxic gas emissions in the air, increases total soil organic carbon, reduces microbial biomass and soil aggregation) and agriculture (increases the success of plant propagation by tissue culture and fertility of plant media and prevent root rot).
Activated charcoal can be distinguished from charcoal based on the nature of the surface. The surface of the charcoal is still covered by hydrocarbon deposits that inhibit its activity, while the surface of the activated charcoal is relatively free from deposits, the surface is wide and the pores have been opened, so it has high absorption. To increase the absorption of charcoal, the material can be converted into activated charcoal through the activation process.
Along with the development of the industry, the need for activated charcoal is also increasing, both for export and domestic needs. Activated charcoal is a product resulting from modified carbonization which has many uses and has been used since the first world war (Austin, 1984). In 2000, Indonesia exported 10,205 tons of activated charcoal with destination countries including Japan, South Korea, Taiwan, Malaysia, Norway, England, France, Germany, China, the Arab Emirates and Sri Lanka (BI, 2000). Furthermore, the Asian and Pacific Coconut Community in Allorerung et al. (2008) reported that the export volume of activated charcoal from Indonesia in 2005 was 25,671 tons.
Although activated charcoal has been used for a long time, until now in general, not many people know how to make and use activated charcoal. For this reason, this paper introduces raw materials, manufacturing methods, processing yields, properties, types and uses of activated charcoal.
Some materials that contain a lot of carbon such as wood, sawdust, seed coat, rice husk, shell, peat, bagasse, coal, lignite and animal bones can be made activated charcoal. However, activated charcoal that is commonly circulated in the market is generally made from coconut shells, wood and coal.
Charcoal which is a residue from the heat decomposition process of materials containing carbon, most of its components are carbon. This thermal decomposition process can be carried out by heating the material directly or indirectly in a heap, kiln or kiln. Most of the charcoal pores are still covered by hydrocarbons, tar, and other components, such as ash, water, nitrogen, and sulfur (Puziy et al., 2003) which inhibit their activity or have low absorption. To activate charcoal into activated charcoal, a retort and steam boiler are used.
Making charcoal is simple, you can use a kiln drum. The kiln drum consists of 3 parts, namely the body and cover of the kiln drum and the chimney. The kiln drum body can be made using a drum that is open at one end (top) and at the other end (bottom) 25 air holes are made with a hole diameter of 1.5 cm. The air hole at the bottom of the drum serves as the first combustion chamber.
At the top of the kiln drum must be opened and made a cover. In the center of the drum cover, a hole with a diameter of 10.2 cm is made, where the hole is used as a place to put the chimney. In order for the kiln drum cover to be easily installed and opened, two handles are installed, each located between the edge and the hole of the kiln drum cover. The chimney is cylindrical with a length of 40 cm and a diameter of 10 cm. To make it easier to install and remove the chimney, on two sides of the chimney, two handles are installed side by side.
At the time of making charcoal, the kiln drum must be placed above the furnace. Therefore, a wall furnace must be made using cement, sand and bricks. The wall furnace is in the form of a ring with an outer diameter of 8 cm larger than the diameter of the kiln drum, 10 cm wide and 10 cm high.
On the side of the furnace, two holes were made facing each other with a size (length x width x height) of 10 x 10 x 10 cm each. To make it easier to close the furnace hole when the combustion process is complete, two manhole covers are made with a size (length x width x height) of 10 x 9.8 x 10 cm each using a mixture of cement and sand made by molding.
C. Making Poses
The process of making activated charcoal is carried out in two stages. The first stage is the process of carbonization of raw materials in a drum kiln to produce charcoal. The second stage is the charcoal activation process using a retort and steam boiler to remove the hydrocarbons that coat the surface of the charcoal so as to increase the porosity of the charcoal.
In both processes the following stages occur:
a. Dehydration is the process of removing water
b. Carbonization is the process of breaking down organic cellulose into carbon elements, and releasing non-carbon compounds
c. Activation is the process of formation and arrangement of carbon so that the pores become larger.
Figure 1. Making charcoal using a kiln drum (left) and making activated charcoal using an electric retort and a laboratory-scale steam boiler (right).
1. Charcoal Making
Charcoal is a porous solid material produced through the pyrolysis (carbonization) process of materials containing carbon. Making charcoal using different raw materials can be done in different ways.
A. Wood charcoal.
To make charcoal from wood raw materials using a kiln drum, the material must be cut into small sizes with a diameter of ± 8 cm and a length of ± 20 cm. The kiln drum is placed on top of the stove and pieces of wood are inserted and arranged so that the kiln drum is not completely filled, or the top of the kiln drum is emptied by about 7.0 cm. Then the fire is lit in the furnace using wood sticks or other fuel.
The fire that is burning in the furnace will enter the kiln drum through the air holes and burn the wood raw materials contained in it. After the wood raw material is lit and it is estimated that it will not go out, the kiln drum is closed and the chimney is installed. Writing is considered complete when the smoke coming out of the chimney is thin and bluish in color. Furthermore, the furnace hole is closed, the chimney is removed and the hole in the kiln drum cover is closed using bricks or other non-combustible covering material.
The bottom edge of the drum furnace must also be covered with sand or soil, so that there are no gaps through which air can enter the kiln drum. When the charcoal in the kiln drum has cooled, the kiln drum cover can be opened and the resulting charcoal can be removed.
B. Shell charcoal
If the raw material for making charcoal uses shell (coconut or candlenut), then the material must be put into the kiln drum in stages (three stages).
In the first stage, the raw material for the shell is fed about a third of the height of the kiln drum. Then the fire is lit in the furnace using wood sticks or other fuel. The fire that is burning in the furnace will enter the kiln drum through the air holes and burn the shell raw materials contained in it. After the raw material for the shell is lit and it is estimated that it will not go out, the kiln drum is closed and the chimney is installed.
After the shell raw material is estimated to have burned completely, the kiln drum cover is opened and the shell raw material is added about one third of the height of the kiln drum. After the addition of shell raw materials is done, the kiln drum is closed again. The addition of shell raw materials into the third stage of the kiln drum is carried out in the same way as the second stage, but efforts are made so that the kiln drum is not full or there is an empty space of about 7.0 cm at the top of the kiln drum.
Writing is considered complete when the smoke coming out of the chimney is thin and bluish in color. Furthermore, the furnace hole is closed, the chimney is removed and the hole in the kiln drum cover is closed using brick or other non-combustible covering material. The bottom edge of the drum furnace must also be covered with sand or soil so that there are no gaps through which air can enter the kiln drum. When the charcoal in the kiln drum has cooled, the kiln drum cover can be opened and the resulting charcoal can be removed.
2. Activated Charcoal Making
Charcoal produced through the carbonization process of raw materials, most of the pores are still closed by hydrocarbons, tar, and other components, such as ash, water, nitrogen, and sulfur, so that their activity or absorption is low. To increase the absorption of charcoal, the material can be converted into activated charcoal through the activation process. In principle, activated charcoal can be made in two ways, namely the chemical method and the physical method. The quality of the activated charcoal produced is highly dependent on the raw materials used, the activating agent, the temperature and the method of activation.
a. Chemical way activation
Activation of the chemical method is principally soaking charcoal with chemical compounds before heating. In the chemical activation process, the charcoal is immersed in an activating solution for 24 hours, then drained and heated at a temperature of 600-900 °C for 1-2 hours. At high temperatures the activating agent will enter between the hexagonal layers and then open the closed surface. Chemicals that can be used are H3PO4, NH4Cl, AlCl3, HNO3, KOH, NaOH, KMnO4, SO3, H2SO4 and K2S (Kienle, 1986).
The use of chemicals as activating agents often results in contamination of the activated charcoal produced. Generally, the activator leaves residues in the form of oxides that are not soluble in water at the time of washing. Therefore, in some processes dissolving with HCl is often carried out to re-bind chemical residues attached to the surface of the activated charcoal and the ash content contained in the activated charcoal. b. Physical activation method Physical activation of charcoal uses weak oxidizing agents, such as water vapor, CO2 gas, N2, O2 and other oxidizing gases.
Therefore, in this process there is no oxidation of the carbon atoms that make up the charcoal, but the oxidizing agent only oxidizes the components that cover the surface of the charcoal pores. This activation principle begins by flowing light gases, such as water vapor, CO2, or air into a retort filled with charcoal and heated at a temperature of 800-1000 °C. At temperatures below 800 °C, the activation process with water vapor or CO2 gas takes place very slowly, while at temperatures above 1000 °C, it will cause damage to the hexagonal charcoal lattice structure (Manocha, 2003).
The manufacture of activated charcoal from charcoal from puspa logs logging waste using a pilot-scale production retort with a capacity of 100 kg equipped with an electric heater was reported by Hendra (2007). Charcoal from puspa wood logging waste is made of 0.5 x 1 x 1 cm, soaked in 5% H3PO4 solution for 24 hours, then drained and put into a retort and then heated at 700 0C.
When the temperature has been reached, hot water vapor (H2O) is flowed from the steam boiler into the retort for 120 minutes at a pressure of 4 bar with a flow rate of 1.5 – 2.5 m/sec. After 120 minutes, the flow of hot steam from the steam boiler into the retort and heating of the retort was stopped and allowed to cool for some time. The activated charcoal produced can only be taken from the retort after it has completely cooled. Lempang et al. (2012) made candlenut shell activated charcoal using a laboratory-scale electric retort. Activated charcoal is made by activating candlenut shell charcoal in an electric retort with a capacity of 500 g.
A total of 300 g of candlenut shell charcoal was put into an electric retort and activated at a temperature of 750 0C using a water vapor activator (H2O) for 120 minutes. After the temperature is reached, hot water vapor (H2O) is flowed from the steam boiler into the retort for 120 minutes at a pressure of 4 bar with a flow rate of ± 2.0 m/s. After 120 minutes, the flow of hot water vapor was stopped and the electric retort was still heated at a temperature of 750 0C for ± 10 minutes so that the water vapor flowing into the retort had evaporated. The heating of the retort is then stopped and left for one night to cool the electric retort and the generated activated charcoal inside.
The yield of activated charcoal processing depends on the raw materials and activation treatment factors (temperature, time and activating ingredients). Coconut shell charcoal which is activated using H2O steam at a temperature of 900-1000 0C for 105 minutes produces activated charcoal with a yield between 36.7-51.5% (Hartoyo et al., 1990).
Activation of candlenut shell charcoal using heat and H2O steam at a temperature of 550-750 0C for 90-120 minutes in an electric retort produces activated charcoal with yields between 56.67-77.33% (Lempang et al., 2012). Meanwhile, candlenut shell charcoal activated with chemicals (H3PO4) and water vapor at a temperature of 750-800 0C for 60 and 90 minutes produced activated charcoal with yields between 47.30-70.80% (Hendra and Darmawan, 2007).
Increasing the activation temperature decreases the yield of activated charcoal. The increasing activation temperature causes the reaction in the retort to be faster and results in an increase in the degradation of the charcoal. The increase in activation time also resulted in a reduced yield of activated charcoal. The longer the activation time, the more parts of the charcoal are degraded. In addition, activation with H2O steam also has an effect on reducing the yield of activated charcoal compared to hot activation. The use of H2O steam in the activation process causes leaching of the hydrocarbons contained on the surface of the charcoal so that the weight of the activated charcoal produced is reduced.
A. Chemical Properties
Activated charcoal does not only contain carbon atoms, but also contains small amounts of oxygen and hydrogen which are chemically bonded in the form of various functional groups, such as carbonyl groups (CO), carboxyl groups (COO), phenols, lactones. and some ether groups.
Oxygen on the surface of activated charcoal, sometimes comes from raw materials or can also occur in the activation process with steam (H2O) or air. This situation can usually cause charcoal to be acidic or basic. In general, activated charcoal raw materials contain mineral components. This component becomes more concentrated during the charcoal activation process. In addition, the chemicals used in the activation process often cause changes in the chemical properties of the resulting charcoal.
B. Physical Properties
Based on physical properties, activated charcoal has several characteristics, including a black solid, tasteless, odorless, hygroscopic, insoluble in water, acids, bases or organic solvents (Hassler, 1974). In addition, activated charcoal is also not damaged due to the influence of temperature or the addition of pH during the activation process.
Activated charcoal has a structure in the form of a twisted network of imperfect carbon layers, which are crossed by an aliphatic bridge. The surface area, dimensions and distribution of carbon atoms that make up the structure of activated charcoal are highly dependent on the raw materials, carbonation conditions and the activation process (Kyotani, 2000). The arrangement of carbon atoms in activated charcoal consists of hexagonal plates.
The pore size of activated charcoal crystallites depends not only on the carbonization temperature but also on the raw materials used. The pore size of activated charcoal can range from 10 to greater than 250 and the pore size is divided into three categories (Buekens et al., 1985 in Rumidatul, 2006), namely:
- Macropores with a diameter greater than 250 with a volume of 0.8 ml/g and a specific surface between 0.5 – 2 m2/g.
- Mesopores with diameters ranging from 50 – 250 with a volume of 0.1 ml/g and a specific surface between 20 – 70 m2/g.
- Micropores that are smaller than 50 in diameter.
Pore size distribution is an important parameter in terms of the ability of activated charcoal to absorb molecules of varying sizes. Besides the pore distribution, the pore shape is a specific parameter for the absorption of activated charcoal that occurs. The pores with a cylindrical shape are easier to close which causes the inactive surface of the activated charcoal. When activated charcoal is used for water purification, more open pores are needed because water mostly contains various kinds of particles.
Figure 2. Activated charcoal of candlenut shell in powder form in packaging
Figure 3. Microphotogram Scanning Electron Microscope (magnification 5000x) on the surface of candlenut shell charcoal (left) and activated charcoal of candlenut shell activated by physics (right) (Lempang et al., 2011)
Capacity Activated charcoal absorption is an accumulation or concentration of components on the surface/interface in two phases. When the two phases interact with each other, a new phase will be formed which is different from each of the previous phases. This is due to the attraction between molecules, ions or atoms in the two phases. This attraction is known as the Van der Walls force. Under certain conditions, atoms, ions or molecules in the interfacial region experience an imbalance of forces, so that they are able to attract other molecules until a balance of forces is reached (Manocha, 2003).
There are several factors that affect the absorption of activated charcoal (Agustina, 2004), namely the nature of the activated charcoal, the nature of the components it absorbs, the nature of the solution and the contact system. The absorption of activated charcoal to components in solution or gas is caused by surface conditions and pore structure (Guo et al., 2007).
Several other literatures report that in general the absorption by activated charcoal is classified as physical absorption. This is due to the large number of activated charcoal pores and large surface area. Another factor that affects the absorption of activated charcoal is the polarity of the activated charcoal surface. These properties vary greatly for each type of activated charcoal, because it really depends on the raw materials, the method of making charcoal and the activating ingredients used.
There are two types of activated charcoal which are distinguished according to their function (Setyaningsih, 1995):
A. Gas adsorbent activated carbon
This type of activated charcoal is used to absorb material in the form of steam or gas. The pores contained in this type of charcoal are micropores which cause gas molecules to be able to pass through, but molecules from liquid cannot pass through. This type of carbon can be found in coconut shell carbon.
B. Liquid-phase activated carbon
This type of activated charcoal is used to absorb unwanted impurities/substances from liquids or solutions. These types of pores of carbon are macropores which allow large molecules to enter. This type of charcoal usually comes from coal and cellulose.
Activated charcoal can be used in various fields, including industry, health, environment and agriculture:
Activated charcoal products are more than 70% used in the industrial sector (Harris, 1999). The main use of activated charcoal is for purification of solutions, such as sugar, syrup, drinking water, vegetables, fats, oils, alcoholic beverages, chemicals and pharmaceutical industries; toxic gas absorbers on masks; deodorizing in the cooling system; absorbing fuel vapor emissions in automotive as well as cigarette filters (Austin, 1984; Harris, 1999).
Activated charcoal has also been used as an additive in products for the maintenance of cleanliness and smoothness of the skin and hair, including soaps, scrubs and shampoos.
Figure 4. Products that use activated charcoal as additives: soap (left), body scrub (middle) and shampoo (right)
In the health sector, activated charcoal is used in the treatment of external poisoning and the treatment of secretonic diarrhea (Muthschler, 1986). In oral poisoning, to avoid absorption of a number of toxins that are still present in the gastrointestinal tract can be done by giving adsorbents. The most efficacious and less harmful adsorbent so that the most widely used is activated charcoal.
According to Muthschler (1986) toxins Cholera, Salmonella and Shigella and pathogenic Coli strains cause increased secretion of electrolytes and water into the intestinal lumen (secretonic diarrhea). Treatment of secretonic diarrhea can be done with the use of adsorbents (eg activated charcoal), developer agents (eg pectin) or astrigens (tanin-containing preparations).
Kadirvelu et al. (2001) has proven the ability of activated charcoal as an adsorbent to metals Hg, Pb, Cd, Ni, Cu in industrial wastewater radiators, nickel plating and copper plating. The ability of activated charcoal as a metal remover is influenced by pH and carbon concentration. The increase in carbon content increases the percentage of activated charcoal adsorption on metal ions. The use of activated charcoal is very important in the water and air purification process Harris (1999). In the process of water purification, activated charcoal in addition to adsorption of metals such as iron, copper. nickel, can also remove odors, colors and tastes contained in solutions or wastewater. In some countries activated charcoal has been reported to have been used as an absorbent for pesticide residues in water purification processes to obtain pesticide-free drinking water (Gerard and Barthelemy, 2003 in Gani, 2007). Activated charcoal can deactivate pesticide contaminants in the soil at doses between 100-400 kg/ha (Miller & McCarty, 2002). Activated charcoal in soil can increase total organic carbon and reduce microbial biomass, respiration, and aggregation as well as the effect of light freezing on the soil, because activated charcoal can absorb and store heat (Weil et al., 2003).
Activated charcoal is used to absorb toxic gases in the paint and adhesive processing industry (Asano et al., 1999) and can reduce formaldehyde emissions from 3.46 mg/l to 0.66 mg/l in the manufacture of particleboard using Urea Formaldehyde as an adhesive. (Santoso and Pari, 2012).
Although research on the use of activated charcoal for agriculture has been widely reported, until now the practice of using activated charcoal in this field has not been widely carried out. The addition of activated bamboo charcoal in the growing media can increase the growth of Eucalyptus urophylla tillers better than the control, but the growth will be better when the activated charcoal is mixed with compost (Gusmailina et al., 2000).
Melina seedling growing media (Gmelina arborea Roxb) added with activated charcoal with a content of 15% can increase the growth of 8.20% in height, 45.95% in stem diameter and 58.82% in biomass weight (Lempang and Tikupadang, 2013). The use of activated charcoal also showed a very significant effect on root growth and biomass weight of the hedgehog pule plant, as well as the development of Capsicum omnium cuttings (Ciner & Tipirdamaz, 2002), as well as preventing root rot in melon plants (Nischwitz et al., 2002).
Activated charcoal is not only used as an additional component in soil media, but can also be used in in vitro culture media. Widiastuty and Martowo (2004) reported that the addition of 2 g/l proanalyzed activated charcoal into Oncidium orchid culture media could increase plantlet height growth, leaf area, number of tillers and number of roots.
Some materials that contain a lot of carbon such as wood, sawdust, seed coat, rice husk, shell, peat, bagasse, coal, lignite and animal bones can be made activated charcoal.
The process of making activated charcoal is carried out in two stages. The first stage is the direct or indirect heating process of raw materials in heaps, kilns or kilns to produce charcoal. The second stage is the process of activating charcoal by physical or chemical means in the retort to produce activated charcoal. Charcoal processing yield
The active ingredients depend on the raw material and activation treatment factors (temperature, time and activating ingredients). Differences in raw materials and activation methods used can cause different properties and qualities of activated charcoal.
Based on its function, activated charcoal is divided into two types, namely gas-absorbing activated charcoal which has micropore-sized pores and is used to absorb material in the form of steam or gas, and liquid-phase activated charcoal which has macropore-sized pores and is used to absorb impurities/substances that are not present. desired from the liquid or solution.
Activated charcoal is used, among others, in the fields of industry, health, environment and agriculture.
Researcher : Mody Lempang
Makassar Forestry Research Institute
Jl. Pioneer of Independence Km.16 Makassar, South Sulawesi, 90243, Indonesia.